I just achieved this annoying achievement earlier today and it took a fair few hours. Although a quarter of my demolition kills were helped via a friend the other three quarters were done by legit means.

As far as I know there are two ways in doing this (Rush game type only):

On Foot - For this I'd pick an assault class. Make sure your primary weapon is a shotgun so that you have C4's equipped and an infinite amount of them thanks to the ammo boxes. Simply plant the C4 in the four corners of a house, it helps to have the extra explosion perk on, and watch it fall. I advise to aim specifically for buildings that house an objective (the little rectangle boxes that emit a flashing red light when a charge is on them)...

Vehicle - I got most of the kills this way. I found the most useful vehicle to be the UAV (although tanks and helicopters work fine), with the extra vehicle damage perk on, this vehicle can take out a building is at least 3 missiles aside the fact it takes forever to reload. Make sure to fire at the front, back and the two sides of a house in order to watch it fall, well-placed missiles can take out 2 walls at once.

Maps with good possibility of gaining a destruction 2.0 kill:

-Isle Inocentes map (first pair of objectives are on an island surrounded by water) the second pair of objectives... there is a building with an objective. This can be taken down with the UAV, however for this I recommend using the helicopter and take charge of the mounted gun and blow away the walls on that thing.

-Valparaiso (jungle map) the area with the last pair of objectives with have a good building to destroy... the building that has mounted weapons on top is a good choice to destroy although this map is long and barely has any destructible buildings; I'd avoid this.

-Arica Harbour (the desert map) The first and second pair of objectives have destructive building potential... Destroying the building that has an objective in the first pair will almost guarantee a kill, make sure you don't shoot the little rectangle office which has the other objective. The second pair of objectives have another building which has potential.

-Port Valdez (snow map) perhaps the best map of them all. Again, the first two pair of objectives seem to have one and two buildings to destory. netting you this achievement. With the first pair, the building is next to a house, you can pick which one you want to destroy first as there is bound to be at least one player in these buildings. The second pair of objectives are both likely to net you a destructible 2.0 kill, just take your time guiding the rockets from the UAV and you should be good.

Notes:
-Using a UAV on a building with an objective it giving you a chance of 3/5 of at least killing ONE guy the destruction 2.0 way.
-Watchtowers can be used but only if a guy is underneath it. Do not shoot it if a player is at the top of the watchtower as this will be classed as suicide cause they will fall to their death not get crushed by the debris.
-Team killing via destruction 2.0 does not count towards the achievement.

Thats how I got it as well. Assault class, shotgun, c4, and lots of patience. Took me bout 150-200 hours to get it, but I got it with no boosting. I figured eventually it would come with time a patience